Mentally impaired by a mutated gene
It is a very rare condition, very similar to autism: fragile X syndrome. You see it slightly more often in boys than in girls. The cause of this intellectual disability is a genetic mutation.
Every year in the Netherlands about fifteen girls and twenty boys are born with fragile X syndrome. As a result of this condition, the patients have a mild to very severe intellectual disability. Because they also often display shy behavior or avoid eye contact, the link with autism is quickly made. This is not entirely justified: in 25 to 33 percent of patients with fragile X syndrome, autism is also diagnosed.
Characteristics
Intellectual disability is not the only characteristic of patients with fragile X syndrome. Language and speech abnormalities such as incoherent speech are common. Furthermore, male patients in particular often display ADHD-like behaviour.
There are also external features such as relatively long faces, large ears, a wide chin and strabismus. Patients also have low muscle tone with overstretched limbs as a result. Furthermore, both gross and fine motor skills of young patients develop more slowly than usual. This is expressed in, among other things, learning to walk later and having difficulty grasping a pen.
Mutation
Fragile X syndrome is caused by a mutation of the FRM1 gene. Genes contain hereditary material. A carrier of genes is a chromosome. X and Y chromosomes are the so-called sex chromosomes: they determine whether someone becomes a man or a woman. Men have an X and a Y chromosome, women have two X chromosomes.
Egg white
The gene FMR1 is located at the end of the long arm of the X chromosome. Due to a mutation, the FMR1 protein is no longer produced. It is not clear why and how the mutation occurs, but it certainly creates a weak connection between the different nerve cells. As a result, signals are no longer properly transmitted and the learning process of the brain is disrupted. This in turn can lead to fragile X syndrome.
The location of FMR1 provides the name for the disease: a breakable (fragile) site in the X chromosome.
Pregnancy
Both men and women can carry the abnormal gene without having fragile X syndrome. Women can pass their mutation on to a child, men most likely not. During pregnancy, chorionic villus sampling or amniocentesis can often be used to check whether women pass on the abnormal gene. In people with intellectual disabilities, fragile X syndrome can eventually be diagnosed with a genetic test.
There is no cure for fragile X syndrome. Treatment is aimed at improving the patient’s quality of life. This includes speech therapy, physiotherapy, educational therapy and medication to reduce the often busy behaviour.
FXTAS and FXPOF
Two conditions are closely associated with Fragile X Syndrome: Fragile X Tremor Ataxia Syndrome (FXTAS) and Fragile X Premature Ovarial Failure (FXPOF). Both conditions can occur in people who carry the abnormal FMR1 gene but do not have fragile X syndrome. FXTAS only occurs in men over the age of 50, FXPOF only in women.
tremble
FXTAS often leads to symptoms that seem more likely to be associated with Parkinson’s disease: trembling movements that cannot be controlled, movement disorders and stiffness in the arms and legs. FXTAS can also lead to several other conditions ranging from burning feet to memory loss and dementia.
Transition
FXPOF is all about one characteristic: an early menopause in women. Often before the age of 40. This means that there is no longer any chance of pregnancy, but it also increases the risk of various health risks such as osteoporosis and cardiovascular disease.
It is estimated that one in three thousand men over the age of 50 have FXTAS. One in a hundred women goes through menopause before the age of 40. It is not clear in which case the FMR1 gene plays a role
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